Pour the milk kefir into the jug of a high powered blender.
Add the frozen berries, maple syrup (if using), and any add-ins of choice.
Blend on high until smooth.
Serve and enjoy.
Notes
Fresh berries: If you want to use fresh berries, you can absolutely do that! Just increase to about 1 ½ cups and/or add a few ice cubes to help thicken it.